Electrical circuitry often must be protected from disruptions caused by electromagnetic interference (EMI) and radio frequency interference (RFI) entering the system. EMI energy can be generated outside of as well as inside the system and can occur anywhere in the electromagnetic spectrum. External EMI energy is an undesired conducted or radiated electrical disturbance that can interfere with the operation of electronic equipment, while internal EMI energy is the unwanted noise or unwanted interference generated by electrical or electronic circuitry within a system.
RFI is now used interchangeably with EMI but generally is limited to interference in the radio communication band. Connectors are particularly susceptible to EMI energy because of the numerous contact areas and openings for cable and external electrical contacts. The art, however, has developed sophisticated electrical connectors having substantial shielding effectiveness against EMI/RFI energy.
Another type of electromagnetic radiation, however, was observed with the development of nuclear explosives. The nuclear explosion, and in some circumstances large scale chemical explosions, produces a sharp surge (large impulse-type) of radio frequency (long wave length) electromagnetic radiation. Unlike EMI/RFI which are localized effects, the intense electric and magnetic fields created by electromagnetic pulse (EMP) energy can damage unprotected electrical and electronic equipment over a wide area. EMP energy consists of a broad spectrum of energies delivered in a fraction of a second. Peak field strengths can reach tens of kilovolts per meter within nanoseconds. These intense pulses induce high voltages and currents which generate a variety of complex electrical events within a system. Damage can range from a momentary interruption of operation to total overload and burn-out of electronic circuits. Multiple pulses of electromagnetic energy generates more damage since electronics can experience local damage from a first pulse which degrades performance and degrades the device or circuits, so that the following pulse results in the complete destruction.
Within every new generation of electronics more components are packed into smaller spaces which makes the circuits more susceptible to EMP damage. This high device packaging-density inhibits the ability to the circuit to conduct away the heat which results from the typical intense, high voltage and current flows generated by an EMP. As a result, there is an increased demand for electrical connectors having protection against EMP and EMI energy threats.
In addition there is also need to protect electronic equipment from power surges owing to electrostatic discharges (ESD). The high voltage generated by ESD can damage voltage sensitive integrated circuits.
One means to protect against EMI, RFI, ESD and EMP energy is by the use of shielding. One such shielding means is disclosed in U.S. Pat. No. 4,330,166. This patent discloses the use of a conductive spring washer seated in the plug portion of the connector so as to make electrical contact with the receptacle portion of the connector when the plug and receptacle are mated. One washer thus provides shielding for a multitude of electrical circuits. For adequate protection, it is essential therefore that there be no break in the continuity of the shielding.
Other means for protecting against power surges include the use of additional specialized circuitry within equipment, such as voltage variable resistors.
It is an object of the present invention to provide a transient suppression device for use with a variety of connectors. It is a further object to include means that can be used to protect each individual circuit from any transient signal. Furthermore, it is an object to provide a minimum inductance ground path thus assuring minimum response time.
It is also an object to provide a transient suppression means that is to be used inside an electrical connector.